Any command line calculator for Ubuntu?

You can use calc. Is not installed by default, but you can install it quickly using the following command:

sudo apt-get install apcalc

After you have installed, you can do any calculation do you wish:

$ calc 5+2
    7
$ calc 5-2
    3
$ calc 5*2          
    10
$ calc 5/2
    2.5
$ calc 5^2
    25
$ calc 'sqrt(2)' 
    1.4142135623730950488
$ calc 'sin(2)'
    0.9092974268256816954
$ calc 'cos(2)'
    -0.416146836547142387
$ calc 'log(2)'
    ~0.30102999566398119521
$ calc 'sqrt(sin(cos(log(2))))^2'
    ~0.81633199125847958126
$ # and so on...

For more information , view its man-page

You can do simple integer arithmetic natively in bash using the ((...)) syntax, e.g.

$ echo $((10000-9000))
1000

There is also the bc calculator, which can accept arithmetic expressions on standard input

$ echo "10000-9000" | bc
1000

The bc program can do floating point arithmetic as well

$ echo "scale = 3; 0.1-0.09" | bc
.01

Bash Arithmetic

Another possible solution is to add a simple function for Bash's built-in arithmetic. Put this in your .bashrc file to try it out:

=() {
    echo "$(($@))"
}

So now, you don't even need $((...)) anymore, just = which seems natural enough.

Replacement

Another thing if you want to be even faster: you can make it replace p with + and x with *. This will work for that:

=() {
    local IFS=' '
    local calc="${*//p/+}"
    calc="${calc//x/*}"
    echo "$(($calc))"
}

= 5 x 5  # Returns 25
= 50p25  # Returns 75

Now you don't even need Shift anymore, the only thing is =  in front of arithmetic.

Hexadecimal output

Output can be displayed in both decimal and hexadecimal, if so desired. (Note: using x substitution will conflict with the 0x... hex syntax)

=() {
    local answer="$(($@))"
    printf '%d (%#x)\n' "$answer" "$answer"
}

Example:

$ = 16 + 0x10
272 (0x110)

$ = 16**3 + 16**4
69632 (0x11000)

Using bc

If you want slightly more advanced calculations, you can pipe it to bc like so:

=() {
    local IFS=' '
    local calc="${*//p/+}"
    calc="${calc//x/*}"
    bc -l <<<"scale=10;$calc"
}

= 'sqrt(2)' # Returns 1.4142135623
= '4*a(1)'  # Returns pi (3.1415926532)

The functions provided by bc are as follows (and can be found in man bc):

sqrt ( expression )
       The value of the sqrt function is the square root of the expression.  
       If the expression is negative, a run time error is generated.

s (x)  The sine of x, x is in radians.

c (x)  The cosine of x, x is in radians.

a (x)  The arctangent of x, arctangent returns radians.

l (x)  The natural logarithm of x.

e (x)  The exponential function of raising e to the value x.

j (n,x)
       The Bessel function of integer order n of x.

It also supports if, for, while, and variables like a programming language. Though it may be better to write to a file if you wanted that.

Keep in mind that it will substitute p and x in function/variable names. It may be better to just remove the replacements.

Using gcalccmd

You can also make the function call gcalccmd (from gnome-calculator) like so:

=() {
    local IFS=' '
    local calc="$*"
    # Uncomment the below for (p → +) and (x → *)
    #calc="${calc//p/+}"
    #calc="${calc//x/*}"
    printf '%s\n quit' "$calc" | gcalccmd | sed 's:^> ::g'
}

= 'sqrt(2)' # Returns 1.4142135623
= '4^4'     # Returns 256

The available functions seem to be (taken straight from the source code), == denotes equivalent functions:

ln()
sqrt()
abs()
int()
frac()
sin()
cos()
tan()
sin⁻¹() == asin()
cos⁻¹() == acos()
tan⁻¹() == atan()
sinh()
cosh()
tanh()
sinh⁻¹() == asinh()
cosh⁻¹() == acosh()
tanh⁻¹() == atanh()
ones()
twos()

Unfortunately, there's no "easier" way to do this. The interactive python interface on the command line is the best suited for what you need, because unlike apcalc\, python is included in Ubuntu. I am not sure if bc is included still, however, python is the hands-down favorite for this stuff.

You can just run the interactive python interface on the command line, and then do math that way. You can use that as your calculator.

To do that, you open the terminal, type python, then hit the Enter button.

Then, in the python prompt that shows up, you can type your math in. For example, 10000 - 9000. The next line output is the result.

If you mean, though, something where you just load the terminal and can do this...

$ 10000 - 9000
1000
$

... then no there's no way to do this in just the terminal without anything else, because Bash doesn't handle numerical arguments like that.

I'd advise you to create a simple function for basic Python calculations. Something like this in your .bashrc:

calc() {
    python3 -c 'import sys; print(eval(" ".join(sys.argv[1:])))' "$@"
}

calc 5 + 5
# Returns 10

result="$(calc 5+5)"
# Stores the result into a variable

If you want to do more advanced math, you can use the following one which imports all of the math module's functions. (see here for more info)

calc() {
    python3 -c 'from math import *; import sys; print(eval(" ".join(sys.argv[1:])))' "$@"
}

calc 'sqrt(2)'  # Needs quotes because (...) is special in Bash
# Returns 1.4142135623730951

result="$(calc 'sqrt(2)')"
# Stores the result into a variable

(Note: Because Python is a programming language, some things may seems strange, e.g. ** for powers of and % for modulo)

Alternatively you can create a Python script calc,

#!/usr/bin/python3
from math import *
import sys
print(eval(' '.join(sys.argv[1:])))

place it in a directory included in the PATH variable and set its executable flag to get the same calc command as above (no need to create a Bash function to run a Python script).

If you want a method in pure Bash, use steeldriver's answer. This answer is only really beneficial if you need the more advanced functions (i.e. from math), as Python is relatively slow compared to Bash.

I'm not sure if this breaks your "switch to python it can do that & I don’t want it in such a way." note, but you don't need to enter the interactive prompt and the result is accessible in Bash so this answer seems valid (to me, at least).

Use the gcalccmd from gnome-calculator (>=13.04) or gcalctool (<13.04) package. I think the package is installed by default

% gcalccmd
> 2+3
5
> 3/2
1.5
> 3*2
6
> 2-3
−1
> 

Here's a quick shell script for this:

#!/bin/bash
echo "$@" | bc

Save this as "c", then put it somewhere in your path (such as /bin), then mark it executable.

# nano /bin/c
# chmod +x /bin/c

From now on, you can run calculations in the terminal like this:

$ c 10000-9000
1000

Another solution I haven't seen mentioned here is Qalculate (qalc).

sudo apt-get install qalc

for the CLI version,

sudo apt-get install qalculate-gtk

for the GUI.

It has a bunch of features such as:

• support for units: e.g. 20 m / s * 12 h = 864 kilom
• built-in constants such as pi, e, c, avogadro
• many built-in functions: e.g. sin(pi) = 0, gamma(4) = 6, 5! = 120, log(1024, 2) = 10
• unit conversion, e.g:

> 120 in
120 * inch = 120 in
> convert cm
120 in = 304.8 centim

• symbolic calculation, e.g. (x + y)^2 = x^2 + 2xy + y^2
• integration, e.g. integrate 3*x^2 = x^3, diff sin(x), pi
• built-in help, e.g. help convert, help integrate
• tab completion of commands
• everything is translated, e.g. my system is in Dutch, so I can write both factorial(5) and faculteit(5).
• and more...

You say you want to use it without prefixes, well... you can use it with a prefix:

$ qalc 5 ft + 3 cm (5 * foot) + (3 * centim) = 1.554 m

as well as running it as a REPL.

Here's a modification of the appropriate part of /etc/bash.bashrc (on Ubuntu 10.04) that will modify the command_not_found handler to run the shell's expression evaluator if the first character of the unknown command is a number or - or +.

You'll be able to do any shell arithmetic this way; see http://www.gnu.org/software/bash/manual/bashref.html#Shell-Arithmetic for a list of arithmetic operators.

Note that if the expression you want to evaluate contains a *, you will have to quote the * with \ or quotes since the shell will do filename expansion before deciding which command to run. Same thing for other operators like >>.

Put this in your ~/.bashrc, then type . ~/.bashrc and try it out.

# if the command-not-found package is installed, use it
if [ -x /usr/lib/command-not-found -o -x /usr/share/command-not-found ]; then
    function command_not_found_handle {
        if [[ $1 == [0-9+-]* ]]; then
           echo $(( $@ ))
        elif [ -x /usr/lib/command-not-found ]; then
           /usr/bin/python /usr/lib/command-not-found -- $1
           return $?
        elif [ -x /usr/share/command-not-found ]; then
           /usr/bin/python /usr/share/command-not-found -- $1
           return $?
        else
           return 127
        fi
    }
fi

Sample output: (I am typing cta, a typo, just to test that our new command_not_found handler will still try to look for unknown commands).

mp@ubuntu:~$ cta
No command 'cta' found, did you mean:
 Command 'cda' from package 'xmcd' (universe)
 Command 'cat' from package 'coreutils' (main)
cta: command not found
mp@ubuntu:~$ 9000-1000
8000

dc! It's part of coreutils, so it's installed on OS X, Ubuntu, and pretty much EVERYTHING else. It's an RPN calculator, so if you don't like those, it's not for you.

Very basic commands are as follows (manpage has all the syntax that I didn't include. Exponentiation, anyone?)

You only need spaces between numbers. They are ignored in all other cases.

Typing a number pushes it to the top of the stack.

+ Adds top 2 items in stack, then pushes result to stack (`2 4 +p` outputs 6)
- Subtracts top 2 items in stack, then pushes result to stack (`4 2 -p` outputs 2)
* Multiplies top 2 items in stack, then pushes result to stack (`6 5 *p` outputs 30)
/ Divides top 2 items in stack, then pushes result to stack (`54 7 /p` outputs 8)
p Print top item in stack, without destroying it
c Clear stack
r Swap top 2 items on stack
d Duplicate top item on stack
k Pops top item off stack, using it to determine precision (so 10 k would print 10 numbers after the decimal point). Default is 0, so it won't do floating point math by default.
n Pops top value off stack, then sends to stdout without a trailing newline
f Dump stack. Useful for finding what something does